Conventionally, in determining the position of a working platform on a sea, two light wave distance measuring instruments set apart on the working platform receive light coming from a fixed light generator located on a land. As the distance between the two distance measuring instruments is known, three sides of a triangle connecting the three points, the fixed light generator and two distance measuring instruments can be known, and this triangle can be specified. Therefore, the position of the working platform can be specified with the fixed light generator as a reference.
A working platform on a sea usually moves and floats vertically as well as horizontally during work due to waves, current, winds, etc. It is very difficult under such conditions to measure the position of the working platform at a hiqh accuracy efficiently in a short period of time. Particularly, it is significantly difficult to always keep the light generator on a land within the field of view of the distance measuring instruments due to rocking of the working platform caused by waves. As such a measuring apparatus, there is proposed a light wave distance measuring apparatus of an automatic tracking type.
As such an automatic tracking type light wave measuring apparatus, as disclosed in, for example, Published Examined Japanese Utility Model Application No. 59-8221, there is known an apparatus constituted as a combination of a collimating light wave distance measuring instrument, which is placed on a movable body such as a platform and has a collimating telescope, mounted at the top or bottom center of a light wave distance measuring instrument body supported rotatable horizontally and rockable vertically in such a way that its optical axis is in parallel to the optical axis of the distance measuring instrument, and has quartersplitted light receiving elements secured at the proximity of the focus of an objective lens of the telescope in such a way that light from a light generator located on a land enters the center of the quarter-splitted light receiving elements, and a received light image originating from collimation deviation intersect perpendicularly in the horizontal and vertical direction of the quarter-splitted light receiving elements to amplify and supply the differential outputs of two pairs of light receiving elements horizontally and vertically facing each other to horizontal and vertical driving motors of a support mechanism of the distance measuring instrument, thus ensuring automatic tracking in the direction of a receiving light source, and a reference light source device, which is fixed, in accordance with the distance between the light wave distance measuring instrument body and the collimating telescope, at an upper portion or lower portion of, and in parallel to the optical axis of, a corner prism provided as a light generator on a land, which prism has a single or composite objective lens or cylindrical lens attached to the front face of a light generator for increasing efficient use of a flux of light and irradiating light in a wide horizontal range and has a flux of signal light from the light generator changed as flicker light by a chopper provided at the front thereof to be distinguished from natural light.
Since the above conventional automatic tracking type light wave measuring apparatus has a collimating light wave distance measuring instrument placed on a platform and a reference light generator on a land which is provided with a chopper for ensuring discrimination between a flux of signal light from a light generator and natural light, it is necessary to provide a battery as a power source for the reference light generator, thus requiring periodic maintenance of the battery, light generator and chopper. Further, since a single or composite objective lens or cylindrical lens is attached to the front face of the light generator for irradiation in a wide horizontal range, the intensity of a flux of light is reduced, making it impossible to ensure automatic tracking for a long distance.
Further, a received light image originating from collimation deviation intersects perpendicularly in the horizontal and vertical direction of the quarter-splitted light receiving elements to amplify the differential outputs of two pairs of light receiving elements horizontally and vertically facing each other. Accordingly, continuous tracking is possible within a narrow range where light coming from the light generator does not deviate from the center of the quarter-splitted light receiving elements, but automatic tracking cannot be provided if the light deviates from the center. Depending on the degree of natural interference, therefore, collimation should frequently be done by an operator.
It is an object of the present invention to provide an automatic tracking type measuring apparatus which overcomes the problems of the conventional apparatus, eliminates the need for maintenance of units provided on a land and provision of a battery and chopper means for discrimination from natural light, and can surely track in a wide range even if units on a platform are located far from units on the land to thereby perform accurate measurement of positioning the platform. Disclosure of the Invention
An automatic tracking type measuring apparatus according to this invention comprises a tracking measuring device having a tracking scanning body and a light wave distance measuring instrument body provided apart from each other vertically at a predetermined space, with their optical axes being parallel to each other and supported integrally rotatable horizontally and rockable vertically, and a reflector device having two corner cube prisms supported in consistency with the predetermined space vertically and with their optical axes being parallel to each other.
According to one aspect of this invention, the tracking scanning body of the tracking measuring device comprises light generating means having a semiconductor light emitting element to irradiate a modulated infrared laser beam from a semiconductor laser; polarizing means for providing circular polarization of a flux of the infrared laser beam irradiated from the light generating means; scanner means for providing plane irradiation of a circular-polarized light spot under control of a predetermined control signal; reflected light discriminating means for discriminating light reflected by the reflector device; and light receiving/sensing means for sensing and converting discriminated reflected light into horizontal and vertical control signals, whereby driving means for horizontal rotation and vertical rocking of the tracking measuring device is controlled by a signal obtained by comparing the control signal of the scanner means to the control signals from the light receiving/sensing means.
According to the tracking type light wave distance measuring apparatus with the above arrangement, for example, two reflector devices are positioned at predetermined positions at a given interval on a land along the coast, with the reflection surfaces facing setting positions on a sea, and two tracking measuring devices having a scanning body for tracking and a light wave distance measuring instrument body are arranged on a platform floating near the setting positions on the sea, at a given interval with their irradiation directions being toward the reflector devices.
When each reflector device located on the land is caught through a collimating telescope provided on the light wave distance measuring instrument body of the corresponding tracking measuring device on the platform, reflected light of light irradiated from the light wave distance measuring instrument body returns to the light wave distance measuring instrument body. After a scanner means control signal is set as a reference, automatic tracking starts.
When an infrared laser beam is emitted by the light emitting means of each tracking scanning body for automatic tracking, each laser beam is subjected to circular polarization by the polarizing means and a circular-polarized light beam is scanned in a plane-irradiation manner by the scanner means and irradiated toward the reflector device.
When each reflector device is caught by such an emitted infrared laser beam within the irradiation range, the beam is reflected in the same direction as incident light by the corner cube prism and the reflected light is discriminated by the discriminating means.
The discriminated reflected light is received and converted into horizontal and vertical control signals by the light receiving/sensing means. These control signals are compared with the reference, i.e., the scanner means control signal to detect horizontal and vertical deviations with respect to the reference bearing of the light wave distance measuring instrument body, whereby the driving means for horizontal rotation and vertical rocking of the tracking measuring device is controlled to cause the bearing of the light wave distance measuring instrument body to coincide with the bearing accurately facing the corner cube prism of the reflector device.
Such an operation is performed automatically and continuously, so that the light wave distance measuring instrument body always faces the reflector device, the distance therebetween is continuously measured, the position of the platform is determined on the basis of this distance, and the platform is moved as needed and is positioned.
Further, according to a second aspect, the tracking scanning body according to the above aspect may comprise light receiving/sensing means which senses reflected light reflected by the reflector device and focused by focusing means and converts it into horizontal and vertical control signals, whereby the driving means for horizontal rotation and vertical rocking of the tracking measuring device is controlled by a signal obtained by comparing the control signal of the scanner means with the control signals from the light receiving/sensing means.
The amount of reflected light received increases by permitting the reflected light to be focused by the focusing means then to be received by the light receiving/sensing means. The received signal is then converted into horizontal and vertical control signals by the light receiving/sensing means. These control signals are compared with the scanner means control signal to detect horizontal and vertical deviations with respect to the reference bearing of the light wave distance measuring instrument body, whereby the driving means for horizontal rotation and vertical rocking of the tracking measuring device is controlled to cause the bearing of the light wave distance measuring instrument body to coincide with the bearing accurately facing the corne cube prism of the reflector device.
Such an operation is performed automatically and continuously, so that the light wave distance measuring instrument body always faces the reflector device, the distance therebetween is continuously measured, the position of the platform is determined on the basis of this distance, and the platform is moved as needed and is positioned.
In the first and second aspects, it is premised that the reflector is included in the field of view of the automatic tracking type measuring apparatus from the beginning. The present invention may further add a search function which can search the reflector in a state where the reflector is out of the field of view, to the automatic tracking type measuring apparatus as the third aspect.
In this case, to perform the searching quickly and surely, a light beam irradiated toward the reflector device from the automatic tracking type measuring apparatus is made to be wider in the vertical direction and searching is carried out only by rotation of the apparatus in the horizontal direction in search mode.
According to this invention, at least one automatic tracking type total station having a transit device further incorporated in the automatic tracking type measuring apparatus having the above structure may be used to provide a measuring system of the position of a platform at a high accuracy as well as quickly and efficiently.
According to the first measuring system, for example, one automatic tracking type total station and a gyro-compass are provided on a platform, and one reflector is placed on a land. This automatic tracking type total station measures the distance between the platform and the reflector and provides an angle between a straight line connecting them and a reference direction set on the platform, while the gyro-compass provides bearing angle representing an angle between the platform and reference direction. Data about these distance, angle and bearing angle is entered into a computer which performs a predetermined computation to position the platform.
According to the second measuring system, two automatic tracking type measuring apparatuses are provided on a platform and two reflectors are provided at a predetermined distance therebetween on a land. One of the two automatic tracking type measuring apparatuses is an automatic tracking type total station having a transit mechanism, which can measure an angle between a line connecting two measuring apparatuses and a line connecting one reflector and one of the measuring apparatuses, for example.
According to thus constituted measuring system, the position of a platform can be measured in a short period of time by simply two automatic tracking type measuring apparatuses and two reflectors alone.
According to the third measuring system, one automatic tracking type total station and one automatic tracking type transit are arranged on a platform. In this case, the automatic tracking type total station measures a distance between it and the first reflector and an angle between a line connecting the reflector and the station and the reference direction of the platform. The automatic tracking type transit measures an angle between the other reflector and the reference direction of the platform.